Shell cartridges

ABSTRACT

The cartridge case contains a principal propellant charge and a shell adapted to the front of the case having a reardwardly open axial cavity filled at least partly by a solid additional propellant charge. The latter is of greater calorific power than the principal propellant charge. A pastille of powder of lower calorific power than the additional propellant charge masks it rearwardly to delay its ignition. The energy from the additional charge is thus applied from the moment when the pressure generated by the main propellant starts to decrease. The performance of the shell is thus improved without generating dangerous excess pressures.

WiliiQ States Patent 1 Birkigt [54] SHELL CARTRIDGES FOREIGN PATENTS OR APPLICATIONS 546,309 9/1956 Belgium 102/40 1 Apr. 3, 1973 OTHER PUBLICATIONS Military Explosives; TM-9-l9l0; Dept. of Army & Air Force; Apr. 1955; pp. 154-158 Priniary Examiner-Robert F. Stahl Attorney-Larson, Taylor & Hinds [57] ABSTRACT The cartridge case contains a principal propellant charge and a shell adapted to the front of the case having a reardwardly open axial cavity filled at least partly by a solid additional propellant charge. The latter is of greater calorific power than the principal propellant charge. A pastille of powder of lower calorific power than the additional propellant charge masks it rearwardly to delay its ignition. The energy from the additional charge is thus applied from the moment when the pressure generated by the main propellant starts to decrease. The performance of the shell is thus improved without generating dangerous excess pressures.

10 Claims, 3 Drawing Figures PATENTEDAPR 3 I975 SHEET 2 BF 2 r coop SHELL CARTRIDGES The present invention relates to improvements in shell cartridges.

The invention relates more particularly to shell cartridges, this expression denoting here, in a general way, any cartridge constituted essentially by, on one hand, a cartridge case containing a propellant charge, and, on the other hand, a shell adapted to the front of the said case, which shell can be of perforating, explosive, incendiary or other character; and it relates more particularly, because it is in this case that its application seems to offer the most advantage, but not exclusively, among these cartridges, to those of small caliber (caliber comprised between 20 and 50 mm, for example) and more particularly again to those with a subcaliber perforating core, such cartridges of small caliber being generally intended to be fired by automatic weapons.v

. It is a particular object of the invention to render the abovesaid cartridges such that they respond better than hitherto with respect-to the various desiderata of practice and, especially, that the performances of the shells (initial speed and range in particular) are improved, all things being otherwise equal.

The cartridge according to the invention comprises a cartridge case containing a principal propellant charge and a shell adapted to the front of the said case and it is characterized in that, on the one hand, the base of the said shell has an axial cavity open towards the rear and occupied, at least in part, by a solid additional propellant charge forming a body with the said base and constituted of a powder of calorific power greater than that i of the abovesaid principal propellant charge,

and, on the other hand, delay means so that the firing of this additional propellant charge is produced with a slight delay (of the order of a millisecond or fraction of millisecond) with respect to the firing of the principal propellant charge,

due to which the major portion at least of the application of useful additional energy due to the combustion of the additional propellant charge comes into play, in the barrel of the launching weapon, from a moment when the pressure generated by the principal propellant charge starts to decrease, which enables benefit to be derived from this application of energy, and from the improvement which thereby results in the performance of the shell, without reaching in the barrel of the launching weapon excess pressures dangerous for the mechanical behavior of the said barrel.

In order that the invention may be more fully understood, two embodiments of cartridges constructed according to the invention are described below purely by way of illustrative but non-limiting examples, with reference to the accompanying drawings in which:

FIG, 1 shows in elevation with axial half cross-section, one embodiment of a shell cartridge of normal caliber constructed according to the invention;

FIG. 2 is a diagram relating to the development of certain pressures in the barrel of the launching weapon as a function of time, this diagram being intended to demonstrate the advantage of the invention, and, finally,

FIG. 3 shows under the same conditions as in the FIG. 1, a shell cartridge with a sub-caliber perforating core constructed according to the invention.

The shell cartridge illustrated in FIG. 1 is a normal caliber shell cartridge, that is to say a cartridge whose projectile (element intended to reach the sighted target) has the caliber of the launching weapon.

slightly less than unity, for example of the order of 95 percent,

and, on the other hand, a shell 3 which can be a perforating, explosive, incendiary, or any other simple or composite type of shell.

Before touching upon the principal features of the invention, it would be opportune to recall, by referring to the diagram of FIG. 2, several conventional ideas on the subject of the development, as a function of time, of the pressure inside the barrel of the firing weapon on the firing of such a cartridge.

In this diagram, there is portrayed, as abscissae, the

time T counted from the beginning of the start of the shot, and expressed in milliseconds, and, as ordinates, the pressure P inside the barrel of the launching weapon expressed in kg/cm2.

In this diagram, the curve 1 represents the development of the pressure generated in the barrel of the launching weapon by the combustion of the principal propellant charge 2. It is seen that this pressure is first increases, then passes through a maximum M (at the end of 1.3 ms in the example considered), then decreases until the moment (time 3.1 ms in the example considered) when the shell emerges from the barrel of the weapon.

Of course, the powder constituting the principal propellant charge 2 is selected so that the maximum M is located below the permissible maximum taking into account the mechanical strength of the barrel of the launching weapon. Thus, for example, the maximum can be situated in the region of 3,000 kg/cm2 if the permissible maximum is of the order of 3,800 kg/cm2.

On this subject, it is interesting to note that, if there is used as principal propellant charge 2, a powder with greater calorific power, for example, with a calorific power of 900 cal/g or more, there will be obtained a curve P of the same general shape as curve P, but whose maximum M would be situated distinctly above the maximum M i.e., in a zone of dangerous excess pressure, and which would decrease more rapidly then gy calculated by the area bounded by the curve P It follows therefore from the preceding considerations that it is not, all things being otherwise equal, by directing efforts towards the adoption, for the principal propellant charge 2, of powders with greater calorific powers, that improvement in performance of the shell 3 could be hoped for by increasing the energy imparted to the said projectile by the combustion of the propellant charge.

The principal feature of the invention has precisely the object of enabling such an improvement to be obtained without running however the risk of dangerous excess pressures in the barrel of the launching weapon.

According to this principal feature, the cartridge constructed as a whole as has just been described is completed by,

on one hand, a solid additional propellant charge 4 housed in an axial cavity 5 fashioned in the base of the shell 3 and open towards the rear, this additional propellant charge 4 forming a body with the said base and being constituted by a powder of greater calorific power than that of the principal propellant charge 2,

and, on the other hand, delay means ensuring the firing of the additional propellant charge 4 with a very slight delay (of the order of a millisecond or fraction of the millisecond) with respect to the firing of the principal propellant charge 2.

There is shown at P on the diagram on FIG. 2, the curve of the pressure denoted by the additional propellant charge 4, which pressure curve starts off upwardly after the curve P passes through a maximum M then decreases slightly, and then remains substantially constant.

There is shown at P.,, the sum of the curves P, and P which illustrates (hatched zone) the gain of energy due to the combustion of the additional propellant charge 4, which gain of energy is situated for the major part in the second half of the time of passage of the projectile in the barrel of the weapon and which does not give rise to exaggerated and dangerous increase in the maximal pressure reached in the said barrel.

As regards the cavity 5, it can be, either a pre-existing cavity such as is frequently found, for ballistic considerations, in the base of shells, or a cavity especially fashioned to receive the additional propellant charge 4.

As for the composition of the said additional propellant charge 4, for which it has been said that it must be of higher calorific power than the principal propellant powder 2, there could be adopted a solid powder having a calorific power of the order of 900 cal/g or even higher. There are known at the present time molded or agglomerated powders having such a calorific power, for example tetryl (2, 4, 6-trinitrophenylnitramine).

Finally, as regards the delay means which have to ensure a deferred firing (initial point A of the curve P of the additional propellant charge 4, they can advantageously be constituted by a retarding relay 6 constructed in the form of a pastille of a powder of lower calorific power than the constituent powder of the abovesaid additional propellant charge 4, this pastille masking rearwardly the additional propellant charge concerned.

In the case of the embodiment illustrated in FlG. 1, the shell 3 is a conventional shell, that is to say a shell of which the whole of the elements participate in the flight towards the objective.

There is shown, in FIG. 3, the application of the invention to a sub-caliber core shell, the said shell comprising essentially a sub-caliber core 7, a base 3a situated behind this core and adapted to accompany the said core at the beginning of the trajectory of the latter and then to separate therefrom, and an envelope 8 externally surrounding the sub-caliber core 7, the abovesaid envelope being arranged so as to be eliminated on firing, a very short distance from the launching weapon, thus liberating the sub-caliber core 7 which pursues alone its flight in the direction of the sighted target.

For such a sub-caliber core cartridge, it is advantageous to provide the base 3a as light as possible and it is hence advantageous to fashion, at the rear of the said base, the housing 5 intended to receive the additional propellant charge 4 as well as, if necessary, the pastille 6 playing the role of retarding relay for the firing of the abovesaid additional propellant charge 4.

As is self evident and as emerges besides already from the preceding description, the invention is in no way limited to those of its methods of application, nor to those of its methods of production of its various parts, which have been more particularly indicated; it embraces on the contrary, all variations and combinations of the above-described features.

What is claim is:

1. Shell cartridge, comprising a cartridge case containing a principal propellant charge; a shell arranged at the front of said case, the base of said shell defining an axial cavity rearwardly open and occupied, at least in part, by a solid additional propellant charge forming a body with said base and constituted by a powder which body is of substantially smaller volume and of greater calorific power than that of said principal propellant charge, the said rearward opening of said cavity being at least as large in cross-section as the maximum cross-section of the said cavity and delay means for delaying the firing of said additional propellant charge of the order of around a millsecond to a fraction of a millisecond with respect to the firing of the principal propellant charge such that the major portion at least of the useful additional energy due to the combustion of the said additional propellant charge takes effect in the barrel of the launching weapon from a moment when the pressure generated by the principal propellant charge starts to decrease, so enabling benefit to be derived from said application of energy and from the improvement which thereby results in the performance of the shell, without reaching in the barrel of the launching weapon excessive pressures dangerous to the mechanical firmness of said barrel.

2. Cartridge according to claim 1, wherein the cavity is a pre-existing cavity fashioned for ballistic considerations.

3. Cartridge according to claim 1, wherein the cavity is especially formed to receive the additional propellant charge.

4. Cartridge according to claim 1, wherein the additional propellant charge is constituted by a solid powder having a calorific power of at least 900 cal/g.

5. Cartridge according to claim 4, wherein the said solid powder is tetryl (2, 4, 6-trinitrophenylnitramine).

6. Cartridge according to claim 1, wherein said delay means are constituted by a delay-relay constructed in the form of a pastille of a powder of lower calorific power then the constituent powder of the abovesaid additional propellant charge, said pastille rearwardly masking said additional propellant charge.

7. Cartridge according to claim 1, wherein said shell is a conventional shell, in which all of the elements participate in the flight towards the target, the cavity being formed at the rear of said shell.

8. Shell cartridge comprising a cartridge case containing a principal propellant charge, a shell arranged at the front of said case, the base of said shell defining an axial cavity rearwardly open and occupied, at least in part, by a solid additional propellant charge forming a body with said base and constituted by a powder which body .is of substantially smaller volume and of greater calorific, power than that of said principal propellant charge, the said rearward opening of said cavity being at' least as large in cross-section as the maximum cross-section of the said cavity and delay means for delaying the firing of said additional propellant charge of the order of around a millsecond to a fraction of a millisecond with respect to the firing of the principal propellant charge such that the major portion at least of the useful energy due to the combustion of the said additional propellant charge takeseffect in the barrel of the launching weapon from a moment when the pressure generated by the principal propellant charge starts to decrease, so enabling benefit to be derived from said application of energy and from the improvement which thereby results in the performance of the. shell, without reaching in the barrel of the launching weapon excessive pressures dangerous to the mechanical firmness of said barrel, wherein said shell is a sub-caliber core shell, comprising essentially a subcaliber 'core, a base situated behind said core and adapted to accompany said shell at the beginning of the trajectory of the latter and to then separate therefrom, and an envelope externally surrounding the sub-caliber core, said envelope being arranged so as to be eliminated on firing, a very short distance from the launching weapon, thus liberating the sub-caliber core which pursues its flight alone in the direction of the sighted target, the cavity intended to receive the additional propellant charge being formed in the above said base.

9. Cartridge according to claim 4, wherein said additional propellant is a one-piece solid. 

1. Shell cartridge, comprising a cartridge case containing a principal propellant charge; a shell arranged at the front of said case, the base of said shell defining an axial cavity rearwardly open and occupied, at least in part, by a solid additional propellant charge forming a body with said base and constituted by a powder which body is of substantially smaller volume and of greater calorific power than that of said principal propellant charge, the said rearward opening of said cavity being at least as large in cross-section as the maximum cross-section of the said cavity and delay means for delaying the firing of said additional propellant charge of the order of around a millsecond to a fraction of a millisecond with respect to the firing of the principal propellant charge such that the major portion at least of the useful additional energy due to the combustion of the said additional propellant charge takes effect in the barrel of the launching weapon from a moment when the pressure generated by the principal propellant charge starts to decrease, so enabling benefit to be derived from said application of energy and from the improvement which thereby results in the performance of the shell, without reaching in the barrel of the launching weapon excessive pressures dangerous to the mechanical firmness of said barrel.
 2. Cartridge according to claim 1, wherein the cavity is a pre-existing cavity fashioned for ballistic considerations.
 3. Cartridge according to claim 1, wherein the cavity is especially formed to receive the additional propellant charge.
 4. Cartridge according to claim 1, wherein the additional propellant charge is constituted by a solid powder having a calorific power of at least 900 cal/g.
 5. Cartridge according to claim 4, wherein the said solid powder is tetryl (2, 4, 6-trinitrophenylnitramine).
 6. Cartridge according to claim 1, wherein said delay means are constituted by a delay-relay constructed in the form of a pastille of a powder of lower calorific power then the constituent powder of the abovesaid additional propellant charge, said pastille rearwardly masking said additional propellant charge.
 7. Cartridge according to claim 1, wherein said shell is a conventional shell, in which all of the elements participate in the flight towards the target, the cavity being formed at the rear of said shell.
 8. Shell cartridge comprising a cartridge case containing a principal propellant charge, a shell arranged at the front of said case, the base of said shell defining an axial cavity rearwardly open and occupied, at least in part, by a solid additional propellant charge forming a body with said base and constituted by a powder which body is of substantially smaller volume and of greater calorific power than that of said principal propellant charge, the said rearward opening of said cavity being at least as large in cross-section as the maximum cross-section of the said cavity and delay means for delaying the firing of said additional propellant charge of the order of around a millsecond to a fraction of a millisecond with respect to the firing of the principal propellant charge such that the major portion at least of the useful energy due to the combustion of the said additional propellant charge takes effect in the barrel of the launching weapon from a moment when the pressure generated by the principal propellant charge starts to decrease, so enabling benefit to be derived from said application of energy and froM the improvement which thereby results in the performance of the shell, without reaching in the barrel of the launching weapon excessive pressures dangerous to the mechanical firmness of said barrel, wherein said shell is a sub-caliber core shell, comprising essentially a sub-caliber core, a base situated behind said core and adapted to accompany said shell at the beginning of the trajectory of the latter and to then separate therefrom, and an envelope externally surrounding the sub-caliber core, said envelope being arranged so as to be eliminated on firing, a very short distance from the launching weapon, thus liberating the sub-caliber core which pursues its flight alone in the direction of the sighted target, the cavity intended to receive the additional propellant charge being formed in the above said base.
 9. Cartridge according to claim 4, wherein said additional propellant is a one-piece solid.
 10. Cartridge according to claim 4, wherein said additional propellant is a compressed powder. 